“Following developments in Ukraine, ratings were reviewed, limits adjusted and additional credit restrictions placed on new business,” the taxpayer-owned bank announced on Friday.

It said it was reviewing its exposure “against any international sanctions”, and that loans to Russian businesses and banks had declined by £100m to £1.8bn.

Authorities have ramped up pressure on the Kremlin by introducing biting sanctions on individuals and businesses. RBS said it had £942m lent out to Russian businesses, £631m to banks and £81m to the government.

The bank repeated warnings that the prospect of Scotland seceding from the UK threatens the taxpayer-owned bank, outlining a series of reasons why a “yes” vote in next month’s referendum could affect its business, including higher borrowing costs, Scotland’s uncertain place in Europe, and the prospect of a new regulatory regime.

“Uncertainties resulting from an affirmative vote in favour of independence would be likely to significantly impact the group’s credit ratings,” RBS said.

“[The uncertainties] could also impact the fiscal, monetary, legal and regulatory landscape to which the group is subject. Were Scotland to become independent, it may also affect Scotland’s status in the EU.

“The occurrence of any of the impacts above could significantly impact the group’s costs and would have a material adverse effect on the group’s business, financial condition, results of operations and prospects.

“The group’s credit ratings would be likely to be negatively impacted by political events, such as an affirmative vote in favour of Scottish independence.”

RBS’s chief executive Ross McEwan has refused to take sides on the independence debate, insisting that the vote is a matter for the Scottish people, although he has said he has a personal view on the matter.

As part of a 9,900-word disclosure of the bank’s legal issues, investigations and reviews, RBS said it was unable to estimate the effect that investigations into foreign exchange market rigging would have, but said that fines and settlements “may be material”.

Mr McEwan has said that any penalties could potentially exceed the £390m RBS paid US and UK authorities for its role in the Libor scandal.

Shares in the bank were trading around 2.6pc down on Friday afternoon.